Pigmented dermatofibrosarcoma protuberans (Bednar tumour): melanocytic colonization or neuroectodermal differentiation? A clinicopathological and immunohistochemical study.

Approximately 5% of cases of dermatofibrosarcoma protuberans contain dendritic melanocytes; such lesions are often known as Bednar tumours. These neoplasms have received little attention in the literature but seem to show no great clinicopathological differences from conventional dermatofibrosarcoma protuberans except for the presence of melanocytes. The existence of such tumours, combined with ultrastructural evidence, has led some leading authors to regard them all as being of neuroectodermal origin. Seven examples of the pigmented variant are presented herein, of which six have been studied immunohistochemically and one has been examined ultrastructurally. Except for the presence of melanocytes in each tumour, no evidence of neuroectodermal (in particular perineural fibroblastic) differentiation has been demonstrated. The histogenesis of dermatofibrosarcoma protuberans and its pigmented variant is discussed. The possibility that the pigmentation may simply reflect secondary melanocyte colonization from the epidermis should be considered.